At a Glance

The IEC 61131-3 Standard (cf. its subclause 1.4) specifies the syntax and semantics of a unified suite of programming languages for programmable controllers. These consist of two textual languages, IL (Instruction List) and ST (Structured Text), and two graphical languages, LD (Ladder Diagram) and FBD (Function Block Diagram).

Additionally, Sequential Function Chart (SFC) language elements are defined for structuring the internal organization of programmable controller programs and function blocks. Also, configuration elements are defined which support the installation of programmable controller programs into programmable controller systems.

NOTE: Control Expert uses the English acronyms for the programming languages.

Further more, features are defined which facilitate communication among programmable controllers and other components of automated systems.

Control Expert compliance to IEC 61131-3

The current version of the Control Expert Programming System supports a compliant subset of the language elements defined in the Standard.

Compliance in this context means the following:

  • The Standard allows an implementer of an IEC Programming System to choose or to drop specific language features or even complete languages out of the Feature Tables which form an inherent part of the specifications; a system claiming compliance to the Standard just has to implement the chosen features according to the specifications given in the Standard.

  • Further on, the Standard allows an implementer to use the defined programming language elements in an interactive programming environment. Since the Standard explicitely states that the specification of such environments is beyond its scope, the implementer has certain degrees of freedom in providing optimized presentation and handling procedures for specific language elements to the benefit of the user.

  • Control Expert uses these degrees of freedom e.g. by introducing the notion of "Project" for the combined handling of the IEC language elements "Configuration" and "Resource". It also uses them e.g. in the mechanisms provided for handling variable declarations or function block instantiations.

IEC standards tables

The supported features and other implementation specific information is given in the following compliance statement and the subsequent tables as required by the Standard.